Metal forming apparatus



Dec. 31, 1963 G. E. PFANNER 3,115,857

METAL FORMING APPARATUS Filed June 5, 1961 2 Sheets-Sheet 1 INVENTOR. G'UIVTHEH E. PFANNER ATTORNEY Dec. 31, 1963 s. E. PFANNER mm. FORMING APPARATUS 2 Sheets-Sheet 2 Filed June 5, 1961 NW N uvmvrm awvmzm J5. PFANNER ATTORNEY 3,115,857 Patented Dec. 31, 1963 [ice 3,115,857 METAL FORMING APPARATUS Gunther E. Pfanner, Lloyd Harbor, N.Y., assignor to Republic Aviation Corporation, Fariningdaie, IN.Y., a corporation of Delaware Filed June 5, 1961, Ser. No. 114,892

6 Claims. (Cl. 113-44) This invention relates to metal working apparatus and particularly to an apparatus for forming metal by electrical capacitor discharge, specifically, induction repulsion.

The present invention contemplates improvements in metal forming techniques by the provision of an apparatus which substantially simplifies metal forming operations with no attendant reduction in quality of the ultimate parts. Thus, comparatively complex and elaborate as sociated equipment, such as presses, matching die sets, and the like, heretofore employed in forming and stamping operations are eliminated.

Additionally, by means of and through the instant invention, forming and stamping operations heretofore considered unfeasible become readily accomplished. For example, relatively large parts, i.e., many feet in transverse dimension, are stamped and formed to ultimate shape and size without requirement of apparatus and structures of prohibitive size and massiveness.

At the same time, the instant apparatus is characterized by its extreme mobility in that it is adapted to be made portable for ready transport to remote work areas. Unlike existing apparatus and equipment, the metal forming element or tool of the present apparatus need not be custom-made and sized to a particular part or range of parts to be worked and formed. On the contrary, the forming tool of the apparatus proposed herein preferably comprises a compact unitary structure that conforms at all times during operation to a preestablished configuration of the ultimate part.

Broadly, induction repulsion has been heretofore proproscd, but its use has been limited to tubular or cylindrical metal parts which have been swaged, pinched, etc., with little or no requirement to control the metal deformation accurately. The desired result has been obtained merely by placing a coil around the tube or cylinder and passing a relatively high current through the coil. The electromagnetic forces created by the current in the coil are directed against the cylinder which is deformed or pinched thereby.

Dies or die elements have also been proposed in prior induction repulsion processes which envision forming sheet metal as well as tubular workpieces to a desired configuration. Thus, relatively flat spiral coils are disposed adjacent the surface of a workpiece in opposition to a die defining the desired surface configuration. The electromagnetic forces produced by the current passing through the coil press localized portions of the workpiece against the adjacent die surface.

It is the purpose of the present invention, among other things, to make feasible for the first time the use of the broad concept of induction repulsion in sheet metal working generally. Thus, forming, stamping, blanking, drawing. and like metal working operations are substantially simplified, and the requirement of matched dies, presses and such equipment is eliminated.

To the above ends, it is herein proposed to fabricate a fiat coil, i.e., one disposed in a single plane, and connected in an electric circuit for the periodic discharge of current therethrough to effect electromagnetic forces of predetermined magnitude against a sheet metal workpiece. This coil is fabricated of resilient metal and adapted to operate in conjunction with a single die element of the prescribed configuration and size whereby the ultimate part is produced. In addition, the flat coil is enclosed or housed within a flexible matrix or blanket, allowing it to conform to and be maintained in intimate contact with the workpiece (with or without an application of external forces in addition to the weight or mass of the encapsulated coil, itself) throughout the forming operation to thereby insure maximum forming force on the workpiece.

The dimensions of the flat coil and its flexible housing relative to the die element and its forming surface configuration are not critical since its effective area will conform thereto. In this way a single, standard unit may be employed regardless of the relative size of the part to be produced. Where the formed area of the part is appreciably larger than the forming surface of the tool, it is pro duced by multiple forming operations, i.e., repeated electromagnetic hammering operations, on the workpiece until such workpiece eventually conforms to and duplicates the forming surface of the die.

With the above and other objects in view as will be apparent, this invention consists in the construction, combination and arrangement of parts all as hereinafter more fully described, claimed and illustrated in the accompanying drawings, wherein:

FIG. 1 is a perspective view of a metal forming tool constructed in accordance with the teachings of the present invention associated with a die block and workpiece to be formed thereby and a circuit diagram to control operation of the tool;

FIG. 2 is a transverse section taken through the tool, workpiece and die block illustrated in FIG. 1 prior to the forming operation;

FIG. 3 is a similar view after commencement of the forming operation;

FIG. 4 is a similar view upon completion of the forming operation; and

FIG. 5 is a plan view illustrative of one coil configuration particularly adapted for deep draw forming operations as contemplated in hemispherical or parabolic type shapes.

Referring more particularly to the drawings, the simplest form of apparatus illustrative of the underlying inventive concept is shown and described to facilitate an understanding thereof. This apparatus comprises essentially a metal forming tool 10 produced by a spiral winding or coil 11, disposed in a single plane and embedded and enclosed within a flexible matrix 12. The coil 11 is fabricated of a metal having high tensile strength and flexibility, preferably, steel cable surrounded by copper wire braid. At its extremities the coil 11 terminates in appropriate junctions 13 for connection by conductors or leads 14 into an electric power circuit 15. At its opposite ends the circuit 15 is grounded as at and includes, in series connection, a source of electribal voltage 16 and a capacitor 17 adapted to be connected and disconnected by a suitable on-otf switch 18. Also in the circuit 15 between the capacitor 17 and the coil 11 is an additional switch means in the form of, for example, a spark gap 19. Electrical voltage from the source 16 is thus supplied to the capacitor 17 and to the adjacent side of gap 19 when switch 18 is closed. A potential difference is thereby established across the spark gap 19. This potential difference is selected at a predetermined value and, upon resistance breakdown of the gap 19, current passes through the coil 11. In this manner periodical discharges of selected value and frequency energize the coil 1.1.

The coil 11 is adapted to work in conjunction with a forming block or die 20 on which a workpiece 21 is disposed and held in place in a conventional manner by means of a restriction plate 22. A forming surface 20' of selected size and shape corresponding to that desired of the ultimate part to be formed is defined by the (lie block 20,-and the workpiece 21 is disposed on the die block 20 overlying this surface 20'. The workpiece 21 is maintained in this position by means of the overlying restriction plate 22 which merely rests upon the workpiece, applying no additional force or pressure thereto, and is held in place by suitable nut and bolt means 24.

The plate 22 is perforated centrally as at 23 to permit the tool 10 to be disposed on and against the workpiece 21 in opposition to the die 20. Upon the discharge of current as above described, the electromagnetic forces created by the current passing through the coil 11 are directed on and against the workpiece, forcing it to conform to the forming surface 20 of the die 20.

During this formaing operation, the resilient coil 11 and its flexible matrix or blanket 12 are held at all times in intimate contact with the surface of the workpiece 21 being formed. To facilitate this, additional means may be employed to operate on and against the tool 10 in opposition to the workpiece 21. This additional means may form an integral part of the tool 10, comprising weight and/or fluid pressure means incorporated in the tool in the form of a chamber adjacent the blanket 12 adapted to contain weighty material or pressurized fluid of selected quantities and value. Rubber blanket forming presses currently being used throughout industry may be employed for this purpose. In any case. however, it is preferred that the means employed to maintain intimate contact between the tool surface and workpiece constitute supplemental means, i.e.. independent means separable from the tool 10. Since this means per se forms no part of the invention, it is illustrated by way of example simply as a number of loosely packed bags 25 of weighty particles such as metal pellets, buckshot, sand, or the like.

For the purpose of a clearer understanding of the inventive concept, the die block 20 and-forming surface 20' are illustrated as relatively small whereby the shape and area of the tool 10 substantially corresponds thereto. It is to be understood that where the part to be formed is of substantial size, the shape and area of the tool 10 would be relatively small. In this case the tool 10 is applied by successive operations to localized areas of the workpiece 21 adjacent the die surface 20' until the ultimate part is eventually formed.

Moreover, in given applications the spacing of the several windings of the coil 11 may be established in a preselected order to concentrate the electromagnetic forces produced thereby on and against selected areas of the workpiece 21. An example of one such spacing is illustrated in FIG. wherein a coil turn configuration is shown that establishes a distance between adjacent portions of the winding that is progressively smaller from the center of the coil outwardly. This coil configuration. retro-spiral, gives superior results in terms of sharper definition and depth when employed in deep-dish type parts such as hemispherical or parabolic shapes required of domes and like parts. Where conical-shaped parts have been produced it has been found that best results are obtained when the winding convolutions are developed into a progressive spiral, i.e., the distance between adjacent portions of the winding is progressively greater from the center of the coil outwardly.

The coil 11 may also be constituted by multiple tiers where greater forming forces are desired. In this case the winding is disposed in the desired number of tiers prior to the development of the next adjacent portion of the winding whereby the resulting electromagnetic forces of the several tiers substantially correspond in magnitude with the adjacent portions of the winding in the tier.

What is claimed is:

1. A metal forming apparatus comprising a die element defining a surface of selected configuration and size, and a resilient coil enclosed within a flexible matrix adapted to rest on and conform to the surface of a metal workpiece in opposition to said die element, and current discharge means connected to said coil and periodically operable whereby the electromagnetic forces accompanying each current discharge through said coil are directed against the workpiece.

2. The apparatus of claim 1 including additional means operative on and against said matrix whereby said coil is maintained a constant distance from the surface of said workpiece at each forming operation.

3. The apparatus of claim 1 wherein said coil is formed by copper-clad steel cable.

4. The apparatus of claim 1 wherein said coil is formed by a winding the adjacent portions of which are spaced one from the other a predetermined distance.

5. The apparatus of claim 1 wherein said coil is formed by a retro-spiral winding.

6. The apparatus of claim 3 wherein said additional means includes a container having resilient walls and filled with a comparatively weighty substance.

References Cited in the file of this patent UNITED sTATEs PATENTS 2,431,943 Land et al Dec. 2, 1947 2,916,771 Lang et a1 Dec. 15, 1959 2,976,907 Harvey et a1 Mar. 28, 1961 FOREIGN PATENTS 489,477 Italy Mar. 28, 1961 

1. A METAL FORMING APPARATUS COMPRISING A DIE ELEMENT DEFINING A SURFACE OF SELECTED CONFIGURATON AND SIZE, AND A RESILIENT COIL ENCLOSED WITHIN A FLEXIBLE MATRIX ADAPTED TO REST ON AND CONFORM TO THE SURFACE OF A METAL WORKPIECE IN OPPOSITION TO SAID DIE ELEMENT, AND CURRENT DISCHARGE MEANS CONNECTED TO SAID COIL AND PERIODICALLY OPERABLE WHEREBY THE ELECTROMAGNETIC FORCES ACCOMPANYING 